Removal and replacement of existing gravity flow sewer pipes becomes necessary when the old pipe collapses or becomes blocked, or when the old pipe dips and sags so as to create flow restrictions. Sewer pipes traditionally have been made with clay, tile or concrete. Existing methods to remove and replace an existing sewer pipe include open excavation, pipe bursting and pipe reaming. Of these three methods, only open excavation, which is the most dominant, can insure that the new pipe will be installed at the proper grade. However, such excavation creates the most disruption within the communities where most replacement work is done.
Pipe bursting and pipe reaming both rely on the existing pipe for line and grade control. If the old existing pipe has dips or sags, these methods will typically follow the old pipe and the same dips and sags will reappear once the new pipe is installed. Pipe bursting and pipe reaming have no way of controlling the grade while installing the new pipe. Another disadvantage of pipe bursting and pipe reaming is the lack of good methods of lubricating the pipe for installation. Therefore, these methods use tools which are typically 1 inch or larger than the outside diameter of the new pipe to reduce the friction during installation of the new pipe. Such larger tools allow the new pipe to float out of grade, causing even more dips and sags within the new pipe, which is much more noticeable at tighter or flatter grades. Accuracy in any installation process for gravity flow sewers is essential for proper flow through the line. These pipe bursting and reaming methods are very limited in the kind of pipe which can be installed and the size of the installation.
Therefore, a primary objective of the present invention is the provision of an improved method for removing and replacing existing gravity flow sewer pipes.
Another objective of the present invention is the provision of an improved method of installing a new gravity flow sewer line.
A further objective of the present invention is the provision of a method to control the pilot stem during the removal and replacement of existing sewer pipes.
Another objective of the present invention is the provision of a method for installing a new sewer pipe by filling the existing sewer pipe with soil slurry material so as to provide a damping effect on the pilot stem while the pilot stem is supported within a vertically drilled hole to greatly reduce flopping, whipping or jumping off of the pilot stem on the support member during the back reaming removal and replacement process of the existing gravity flow sewer pipe.
Still another objective of the present invention is the provision of a method for supporting a boring tool during the back reaming process of the old existing sewer pipe so as to overcome gravity drop of the tooling to eliminate dips and sags in the replacement sewer pipe.
Another objective of the present invention is the provision of a method of removing old existing sewer pipe by filling the pipe with soil slurry material, grinding the pipe into particles, and forcing the slurry and pipe particles upwardly into vertically drilled holes, and vacuuming the mixture from the holes.
A further objective of the present invention is the provision of a method of removing and replacing an existing sewer pipe having close tolerance of not more than ½″ between a bored hole that removes the old pipe and the new pipe outside diameter.
Still another objective of the present invention is the provision of a sewer pipe replacement method wherein any type of new pipe can be used and much larger pipe sizes can be installed.
Yet another objective of the present invention is the provision of an improved method of forming a trenchless flow line which is accurate and cost effective.
These and other objectives will become apparent from the following description of the invention.